If history repeats itself, you can blame cliodynamics. The so-called
"science of history" is created by Peter Turchin, who specializes
in population dynamics at the University of Connecticut in Storrs:

For the past 15 years, Turchin has been taking the mathematical
techniques that once allowed him to track predator–prey cycles
in forest ecosystems, and applying them to human history. He has analysed
historical records on economic activity, demographic trends and outbursts
of violence in the United States, and has come to the conclusion that
a new wave of internal strife is already on its way1. The peak should
occur in about 2020, he says, and will probably be at least as high
as the one in around 1970. “I hope it won't be as bad as 1870,”
he adds.

Turchin's approach — which he calls cliodynamics after Clio,
the ancient Greek muse of history — is part of a groundswell of
efforts to apply scientific methods to history by identifying and modelling
the broad social forces that Turchin and his colleagues say shape all
human societies. It is an attempt to show that “history is not
'just one damn thing after another'”, says Turchin, paraphrasing
a saying often attributed to the late British historian Arnold Toynbee.

It's possible to fit a model to post-dict (to coin a term) the past without having any real predictive power. If this guy's models can predict the future of our Syrian, Iranian, and North Korean friends, it'll help provide credence for predictions of US society taking until 2020+ before returning to politeness.